The present invention relates to a method and apparatus thereof for detecting a utilization status of an optical disc, and more particularly, to a method and apparatus thereof for identifying a true overwrite area and a true blank area of an optical disc.
An optical disc drive can be used for recording and/or reproducing data onto and/or from the optical discs. The optical disc drive can emit a laser beam from a light source such as a laser diode onto the recording layer of an optical disc, detect the intensity of light reflected back from the optical disc, and convert the light signal into a radio frequency (RF) signal for further signal processing. The RF signal is used to identify which section of the optical disc has been recorded or occupied according to conventional detecting methods. In the conventional method, only AC component of the RF signal is used for detection purpose. According to RF AC component, the status of an optical disc can be divided into three distinct types: blank, data and overwrite.
The drawback of the conventional method is that, if sections of the optical disk have been overwritten, the blank detection quite easy mistakenly detected those sections as the blank area. As a result, it causes erroneously overwriting and eventually causes the whole disk can not be functioned properly. The examples, such as recordable digital versatile discs (DVD−R, DVD+R) and recordable compact discs (CD-R), would be quite often not detecting the correct the optical disc status according to traditional detecting method while performing the process of a next writable address (NWA) detection or the calibration of related servo signal. Thus, it is essential to provide a precision detection method for correctly determining that the position, where is pointed on by the optical pickup unit (OPU), has been previously recorded.
A traditional blank detection circuit provides blank flags by using mono-multi or other means to achieve the purpose. This kind of blank detection circuit, however, often identifies some of overwrite areas as blank areas. As a result, the overwrite area on the optical disc may be etched again by write pulses due to the misjudgement of the blank detection. Thus, the conventional blank detecting method has limited ability to indicate overwritten areas with reference to the RF AC signal only.